In class on Friday, we talked about Plate Tectonics and the Rock Cycle. For most of us, it was a throwback to middle school science, but there are some key points that are good to review:
- You can think of the earth like an egg. The shell, like earth’s crust, is the tough outside layer. Under the crust is the fluid mantle, like the white of an egg. This layer is constantly in motion. In the mantle, the magma approaches the hot core, rises, cools near the crust, sinks, and repeats this cycle. The innermost part of earth, like the yolk, is the core. The earth’s core is made of an inner and outer core. The outer core is still fluid, while the inner core is solid. The core is made up of mostly iron and nickel, which is the cause of the magnetic fields around earth.
- Earth is thought to be made up of about 12 tectonic plates.
- These plates float on the earth’s mantle, and subsequently move. Below is a picture of the tectonic plates that make up earth.
- These plates move in three different ways. First, they can diverge. This occurs when two plates spread apart from one another. Magma from the mantle comes up to fill the space between the plates and creates new crust as it cools. This forms mid-ocean ridges. The second type of movement is called convergence. When one plate becomes denser than the underlying mantle, it sinks back into the earth. This is called subduction. Subduction occurs at plate boundaries when the two plates collide. The third type of movement is on a transform fault. This process occurs when plates slide horizontally against each other. When this occurs along plate boundaries in the ocean, small earthquakes occur. However, when transformation occurs along fault lines under land, huge, destructive earthquakes can result.
- If you need more detail or clarification, refer to the handout given in class.
The Rock Cycle:
- The three types of rock are: igneous, sedimentary, and metamorphic. Through processes of heating, cooling, melting, and squashing, the rocks change from one type to another.
- Also crucial to the process is weathering, which causes the breakdown of igneous and metamorphic rock and the creation of sedimentary.
If anyone has any questions or comments, feel free to ask!